|
|
PDF LTC3410-1.875 Data sheet ( Hoja de datos )
| Número de pieza | LTC3410-1.875 | |
| Descripción | 2.25MHz/ 300mA Synchronous Step-Down Regulator | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
|
Hay una vista previa y un enlace de descarga de LTC3410-1.875 (archivo pdf) en la parte inferior de esta página. Total 16 Páginas | ||
|
No Preview Available !
FEATURES
■ High Efficiency: Up to 93%
■ Very Low Quiescent Current: Only 26µA
■ Low Output Voltage Ripple
■ 300mA Output Current at VIN = 3V
■ 380mA Minimum Peak Switch Current
■ 2.5V to 5.5V Input Voltage Range
■ 2.25MHz Constant Frequency Operation
■ No Schottky Diode Required
■ Stable with Ceramic Capacitors
■ Shutdown Mode Draws < 1µA Supply Current
■ ±2% Output Voltage Accuracy
■ Current Mode Operation for Excellent Line and
Load Transient Response
■ Overtemperature Protected
■ Available in Low Profile SC70 Package
U
APPLICATIO S
■ Cellular Telephones
■ Wireless and DSL Modems
■ Digital Cameras
■ MP3 Players
■ Portable Instruments
LTCwww3.D4at1aS0he-e1t4U..8co7m 5
2.25MHz, 300mA
Synchronous Step-Down
Regulator in SC70
DESCRIPTIO
The LTC®3410-1.875 is a high efficiency monolithic syn-
chronous buck regulator using a constant frequency,
current mode architecture. Supply current during opera-
tion is only 26µA, dropping to <1µA in shutdown. The 2.5V
to 5.5V input voltage range makes the LTC3410-1.875
ideally suited for single Li-Ion battery-powered applica-
tions. 100% duty cycle provides low dropout operation,
extending battery life in portable systems.
Switching frequency is internally set at 2.25MHz, allowing
the use of small surface mount inductors and capacitors.
The LTC3410-1.875 is specifically designed to work well
with ceramic output capacitors, achieving very low output
voltage ripple and a small PCB footprint.
The internal synchronous switch increases efficiency and
eliminates the need for an external Schottky diode. The
LTC3410-1.875 is available in a tiny, low profile SC70
package.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners. Protected by U.S. Patents,
including 5481178, 5994885, 6127815, 6304066, 6498466, 6580258, 6611131.
TYPICAL APPLICATIO
VIN
2.7V
TO 5.5V
CIN
4.7µF
CER
VIN SW
LTC3410-1.875
RUN
VOUT
GND
4.7µH
VOUT
1.875V
COUT
4.7µF
CER
34101875 TA01
Efficiency and Power Loss vs
Output Current
100
90 EFFICIENCY
VIN
80
2.7V
4.2V
70
3.6V
60 3.6V
1
0.1
50 0.01
40
30
20
4.2V
10
2.7V
POWER LOSS
VIN
0.001
0
0.1 1
0.0001
10 100 1000
OUTPUT CURRENT (mA)
34101875 TA02
34101875f
1
1 page  
LTCwww3.D4at1aS0he-e1t4U..8co7m 5
TYPICAL PERFOR A CE CHARACTERISTICS
(From Figure 1)
Burst Mode Operation
Start-Up from Shutdown
SW
5V/DIV
VOUT
50mV/DIV
AC COUPLED
IL
100mA/DIV
VIN = 3.6V
ILOAD = 10mA
2µs/DIV
34101875 G13
RUN
2V/DIV
VOUT
1V/DIV
IL
200mA/DIV
VIN = 3.6V
200µs/DIV
ILOAD = 300mA
34101875 G14
Start-Up from Shutdown
RUN
2V/DIV
VOUT
1V/DIV
IL
200mA/DIV
VIN = 3.6V
ILOAD = 0A
200µs/DIV
34101875 G15
Load Step
VOUT
100mV/DIV
AC-COUPLED
IL
200mA/DIV
ILOAD
200mA/DIV
10µs/DIV
VIN = 3.6V
ILOAD = 0mA TO 300mA
34101875 G16
Load Step
VOUT
100mV/DIV
AC-COUPLED
IL
200mA/DIV
ILOAD
200mA/DIV
10µs/DIV
VIN = 3.6V
ILOAD = 15mA TO 300mA
34101875 G17
34101875f
5
5 Page 
LTCw w3w4.1D0a-1t a.8S 7h 5e e t 4 U . c
APPLICATIO S I FOR ATIO
Thermal Considerations
In most applications the LTC3410-1.875 does not dissi-
pate much heat due to its high efficiency. But, in applica-
tions where the LTC3410-1.875 is running at high ambient
temperature with low supply voltage, the heat dissipated
may exceed the maximum junction temperature of the
part. If the junction temperature reaches approximately
150°C, both power switches will be turned off and the SW
node will become high impedance.
To prevent the LTC3410-1.875 from exceeding the maxi-
mum junction temperature, the user will need to do some
thermal analysis. The goal of the thermal analysis is to
determine whether the power dissipated exceeds the
maximum junction temperature of the part. The tempera-
ture rise is given by:
TR = (PD)(θJA)
where PD is the power dissipated by the regulator and
θJAis the thermal resistance from the junction of the die to
the ambient temperature.
The junction temperature, TJ, is given by:
TJ = TA + TR
where TA is the ambient temperature.
As an example, consider the LTC3410-1.875 with an input
voltage of 2.7V, a load current of 300mA and an ambient
temperature of 70°C. From the typical performance
graph of switch resistance, the RDS(ON) of the
P-channel switch at 70°C is approximately 1.05Ω and
the RDS(ON) of the N-channel synchronous switch is ap-
proximately 0.75Ω. The series resistance looking into the
SW pin is:
RSW = 1.05Ω (0.69) + 0.75Ω (0.31) = 0.96Ω
Therefore, power dissipated by the part is:
PD = ILOAD2 • RDS(ON) = 86.4mW
For the SC70 package, the θJA is 250°C/ W. Thus, the
junction temperature of the regulator is:
TJ = 70°C + (0.0864)(250) = 91.6°C
which is well below the maximum junction temperature
of 125°C.
Note that at higher supply voltages, the junction tempera-
ture is lower due to reduced switch resistance (RDS(ON)).
Checking Transient Response
The regulator loop response can be checked by looking at
the load transient response. Switching regulators take
several cycles to respond to a step in load current. When
a load step occurs, VOUT immediately shifts by an amount
equal to (∆ILOAD • ESR), where ESR is the effective series
resistance of COUT. ∆ILOAD also begins to charge or dis-
charge COUT, which generates a feedback error signal. The
regulator loop then acts to return VOUT to its steady-state
value. During this recovery time VOUT can be monitored for
overshoot or ringing that would indicate a stability prob-
lem. For a detailed explanation of switching control loop
theory, see Application Note 76.
A second, more severe transient is caused by switching in
loads with large (>1µF) supply bypass capacitors. The dis-
charged bypass capacitors are effectively put in parallel
with COUT, causing a rapid drop in VOUT. No regulator can
deliver enough current to prevent this problem if the load
switch resistance is low and it is driven quickly. The only
solution is to limit the rise time of the switch drive so that
the load rise time is limited to approximately (25 • CLOAD).
Thus, a 10µF capacitor charging to 3.3V would require a
250µs rise time, limiting the charging current to about
130mA.
34101875f
11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet LTC3410-1.875.PDF ] | |
Hoja de datos destacado
| Número de pieza | Descripción | Fabricantes |
| LTC3410-1.875 | 2.25MHz/ 300mA Synchronous Step-Down Regulator | Linear Technology |
| Número de pieza | Descripción | Fabricantes |
| SLA6805M | High Voltage 3 phase Motor Driver IC. |
 Sanken |
| SDC1742 | 12- and 14-Bit Hybrid Synchro / Resolver-to-Digital Converters. |
 Analog Devices |
|
DataSheet.es es una pagina web que funciona como un repositorio de manuales o hoja de datos de muchos de los productos más populares, |
| DataSheet.es | 2020 | Privacy Policy | Contacto | Buscar |